1. Field of the Invention
The present invention relates to a variable resistance control and, more particularly, to a variable resistance slide control having a slider that is movable rectilinearly in the housing.
2. Description of the Prior Art
Variable resistance slide controls that are provided with a slider carrying a contactor member that wipingly engage a resistance element and a collector member are well known in the art, some of such controls being exemplified in U.S. Pat. Nos. 3,588,779; 3,732,521 and 3,735,327. In certain of these prior art slide controls, the housing is made from two substantially identical molded half sections joined to leave a slot in the front wall of the housing, and a slider having a handle portion extending through the slot constrains a contactor member to wipingly engage the resistance element and collector member that are mounted in the housing. The slider bears on the front wall of the housing of the joined half sections defining the slot and, during movement rectilinearly along the slot, the slider frequently jumps, skips or rocks. This erratic motion of the slider is caused in part by misalignment of the two spaced surfaces of the front wall that are formed upon joining together the two half sections of the housing, thus causing the slider to bear unevenly on the surfaces supporting the slider. Erratic motion of the slider is also partially caused by the large tolerances required in the manufacture and assembly of the half sections of the housing and slider. It would therefore be desirable to provide a variable resistance slide control having smoother and more uniform slider movement.
Prior art slide controls are provided with an elongated longitudinal slot through which the handle portion of the slider projects. Various means have been suggested for closing the slot in order to prevent exposure of the resistance element and prevent ingress of harmful objects into the control. Generally, such closing means increases the cost and complexity of manufacture. The slide control shown in U.S. Pat. No. 3,887,892, assigned to the same assignee as the present invention, attempts to solve this problem by moving the longitudinal slot from the front wall to a side wall, the front wall serving as a guide rail for the slider. This has presented difficulties because the front wall, being made from a metal stamping, is not free from burrs and other deformities and therefore causes the slider to be subject to binding. It is therefore desirable to provide a variable resistance slide control that can be assembled and manufactured in a simple and facile manner, that is protected against the ingress of foreign materials into the housing, and wherein the plastic slider rides upon a polished plastic surface of compatible material to prevent binding.
Prior art controls as shown in U.S. Pat. No. 3,887,892 utilize the dielectric base as a side wall of the housing. The collector member and the terminals of the resistance element are crimped through apertures in the base and are exposed on the outside surface. These controls, when mounted near a metal chassis or the like, require additional external insulation means to prevent shorting of the terminals to the external structures. It is therefore desirable to provide economical protection for such controls to prevent such shorting.
Prior art slide controls, as exemplified in U.S. Pat. Nos. 3,735,327; 3,732,521 and 3,887,892, are provided with a contactor member which is mounted and supported to the slide at a formed portion. A formed structure cannot be as accurately produced as a stamped or blanked structure because the size and shape of a blanked part is precisely defined by a matching punch and die whereas formed contours include some variation from spring-back of the material. The use of a blanked portion of the contactor member for locating the contactor member with respect to the slider improves the accuracy of positioning and controlling the contactor member. It is therefore desirable to provide a slide control wherein the contactor member is supported and guided by the slide at a blanked portion of the contactor member.